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B.C. clams reveal an ancient secret (with video)

Man-made ‘gardens’ shown to dramatically increase size of shellfish

First Nations man-made “clam gardens” dramatically increase the survival, growth rate and size of shellfish using materials as simple as boulders and crushed shells, according to a new study by researchers at Simon Fraser University and the University of Washington.

First Nations “clam gardens” dramatically increase the survival, growth rate and size of shellfish using materials as simple as boulders and crushed shells, according to a new study by researchers at Simon Fraser University and the University of Washington.

A collaborative project by marine ecologists and archeologists studied clam growth in ancient stone-walled beach terraces created over the last few thousand years. The team recorded four times as many butter clams and twice as many littlenecks in clam gardens compared with unaltered beaches.

To test the effect, researchers first had to find nearby clam beaches that had not already been modified for clam cultivation, which was a bigger challenge than they expected.

Marine ecologist Anne Salomon recalled canoeing along the beaches at Quadra Island and being stunned at the number and extent of clam gardens clearly visible in Kanish Bay during a summer low tide.

“Within 80 canoe strokes we saw one, we saw another, we saw another; there they all were, about 10 of them in 20 minutes,” she said. “Every place where you could put a clam garden, they were there.”

Human-engineered clam gardens have been recorded from Washington state all the way up to Alaska and in many locations throughout the world, including Russia. But the quality of the surviving clam gardens and the availability of local knowledge of First Nations people here in B.C. is a rare combination, according to co-author Dana Lepofsky.

The success of aquaculture as practised by First Nations people over thousands of years provides valuable insights for modern conservation and resource management, according to the study led by graduate student Amy Groesbeck.

Access rights to clam gardens and management knowledge were likely passed down through First Nations families in the same way as fishing and hunting rights, giving people a generational stake in the sustainability of the resource.

Long-term community management of resources discourages over-harvesting and other destructive practices, Salomon said.

The study was published this week in the online peer-reviewed journal of the Public Library of Science.

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